Biomedical subjects

David F Wilson

Publications and source records attributed to David F Wilson.

42 records · Page 3Linked to original sources

PubMed2002

A method for measuring oxygen distributions in tissue using frequency domain phosphorometry.

Phosphorescence lifetime of phosphors dissolved in biological fluids is dependent on the local oxygen concentration. When phosphor is added to the blood in vivo there is a distribution of lifetimes due to the distribution of oxygen concentrations in the blood of the sampled tissue volume. The distribution of oxygen can be assessed non-invasively and in practically real-time using frequency domain time-resolved phosphorometry. Here we describe a multi-frequency system for measurements of oxygen distributions in tissue in vivo.

Entropy↗

PubMed2002

Measurement of tumor oxygenation using new frequency domain phosphorometers.

Oxygen dependent quenching of phosphorescence allows for non-invasive measurements of oxygen in tissue. We have designed and constructed a novel multi-frequency instrument for measurement of phosphorescence lifetimes and developed algorithms for determining the distribution of oxygen (oxygen histogram) in the microvasculature of tissue with good temporal resolution (Vinogradov et al., 2002, Compar. Biochem. A, these proceedings). This technology, in combination with a new water soluble near infra red phosphor (Oxyphor G2), was used to examine the oxygenation of subcutaneous Q7 tumors grown on the flank of Buffalo rats and their response to giving the rats oxygen or carbogen to breathe. Phosphorescence was measured using excitation at 635 nm and emission at >700 nm (the phosphorescence maximum is near 800 nm). The excitation and collection light guides were placed on the surface of the skin of the anesthetized animals separated by approximately 0.8 cm. A 6 x 6 or 7 x 7 grid (approx. 4 cm x 4 cm) was drawn on the flank and oxygen histograms were measured in each square, providing 'images' of the oxygen distribution in the tissue. This procedure determines the tissue oxygen distribution at each position in the grid. Regions of relative hypoxia (associated with the tumor) can be readily localized and the extent of hypoxia quantitatively evaluated.

Algorithms↗

PubMed2002

Preliminary ossiculoplasty results using the Kurz titanium prostheses.

OBJECTIVE: Limitations in biocompatibility and hearing improvement with ossicular chain reconstruction prostheses are addressed with new, lightweight titanium prostheses designed to maximize visualization of the capitulum and footplate regions. The effectiveness of these new prostheses is being tested in a prospective multicenter study. STUDY DESIGN: Prospective case series. SETTING: Multicenter (8 sites), primarily tertiary private practice or academic otologic clinics. PATIENTS: A convenience sample of 31 patients undergoing ossiculoplasty, with 16 partial ossicular chain reconstructions using the Bell prosthesis and 15 total reconstructions using the Aerial prosthesis. INTERVENTION: Ossiculoplasty using new Kurz titanium prostheses. Cartilage was interposed between the tympanic membrane and the prosthesis. MAIN OUTCOME MEASURES: Air-bone gap for pure tone average and 3,000 and 4,000 Hz, assessed preoperatively and 3 months, 6 months, and 12 months postoperatively; percent of patients obtaining an air-bone gap of </=20 dB; high-frequency average (1,000, 2,000, and 4,000 Hz) to evaluate sensorineural hearing loss; and extrusion rate. RESULTS: A postoperative air-bone gap of </=20 dB was obtained in 81% of Bell prosthesis patients and 67% of Aerial prosthesis patients at 3 months. The results were stable to improved for later time intervals. High-frequency gaps were similar to the pure tone average gap. To date, there have been no instances of extrusion, and all the surgeons found the prostheses easy to use and thought that the design characteristics facilitated accurate placement. CONCLUSIONS: Initial evaluation of the Kurz titanium prostheses produced low extrusion rates (none to date) with excellent hearing results, including good high-frequency conduction. Good visualization and accurate placement were easy to achieve. Further studies are needed to confirm long-term efficacy.

Audiometry, Pure-Tone↗

PubMed2002

Syndecan-1 expression during postnatal tooth and oral mucosa development in rats aged from two days to six weeks.

Syndecans are a family of heparan sulphate proteoglycans that regulate cell-matrix interactions that influence cell growth, proliferation and morphology. The aim of this study was to observe changes in the expression of Syndecan-1 in the developing epithelium of the rat oral mucosa and in the epithelial cell rests of Malassez in the developing periodontium of normal rat molars, from late crown development through to early eruption. Immuno-histochemistry (Syndecan-1 N-18) and histochemistry (Alcec Bluel were used to observe changes in the expression of Syndecon-1 in rats aged two to 42 days. Results indicated that during normal tooth development in the rat, labelling or staining of variable intensity for Syndecan-1 was demonstrated in the stratified oral epithelium above the stratum basale in the rat tongue and palate, and in ameloblasts of the developing molar in rats aged two to 14 days. Histochemical staining of the predentine and dentine layers was consistent in all specimens. Labelling or staining for Syndecan-1 was negative in the rat periodontal ligament, which may suggest that either Syndecan-1 was not expressed during normal molar root development or that continued work is required for identification of a suitable label in rats.

Ameloblasts↗

PubMedDate not supplied

Dysgeusia and cholesteatoma.

OBJECTIVE: To describe an individual with cholesteatoma whose sole presenting symptom was dysgeusia. STUDY DESIGN: Case report. METHOD: A retrospective review of an individual presenting with dysgeusia without any hearing loss, otorrhea, or imbalance who was found to have chronic otitis media with cholesteatoma. RESULT: Surgical exploration confirmed the presence of cholesteatoma and identified an intact but attenuated chorda tympani nerve. The dysgeusia persisted after surgery. CONCLUSION: The anatomical course of the chorda tympani and the usual routes of expansion of cholesteatoma sacs indicates a higher incidence of dysgeusia with cholesteatoma. Further elucidation is necessary to determine the true incidence of this complaint with cholesteatoma.

Adult↗

PubMedDate not supplied

Effect of theophylline and aminophylline on transmitter release at the mammalian neuromuscular junction is not mediated by cAMP.

1. Theophylline and aminophylline have been widely used as inhibitors of phosphodiesterase when examining the role of cAMP in regulating cell function. In reality, however, these phosphodiesterase inhibitors may have additional sites of action that could complicate the interpretation of the results. These additional sites of action could include antagonism of inhibitory adenosine autoreceptors and release of intracellular calcium. The purpose of the present study was to determine which of the above three is the primary mechanism by which theophylline and aminophylline affect transmitter release at the mammalian neuromuscular junction. 2. Quantal release measurements were made using intracellular recording techniques. A variety of drugs were used to elucidate this pathway. Isoproterenol, an adenylate cyclase activator, was first used to establish the effect of enhanced levels of cAMP. Theophylline application on its own or in the presence of a drug combination that blocked the adenosine receptor and phosphodiesterase pathways caused significant release depression, opposite to what is expected if it was functioning to enhance cAMP levels. However, when applied in the presence of a drug combination that blocked the adenosine receptor, phosphodiesterase and intracellular ryanodine calcium pathways, theophylline was unable to depress release. Therefore, it was concluded that the major mechanism of action of theophylline is depression of transmitter release by causing the release of intracellular calcium. 3. Aminophylline application alone resulted in a significant enhancement of release. However, when coupled with an adenosine receptor blocker, the ability of aminophylline to enhance transmitter release was blocked, suggesting that its dominant mechanism of action is adenosine receptor inhibition. 4. Taken together, these results indicate that the use of theophylline and aminophylline is inappropriate when examining the role of cAMP at the mammalian neuromuscular junction.

Action Potentials↗